Effect of bio-asphalt as additive on macro and micro properties of TLA modified asphalt and its modification mechanism

Trinidad Lake Asphalt (TLA) modified asphalt has excellent high temperature performance, but its low temperature performance is poor, which limits its engineering application. But bio-asphalt presents relatively excellent low temperature performance. In this paper, TLA and Bio-asphalt were used as additives to prepare composite modified asphalt with excellent properties both at high and low temperatures. The micro modification mechanism of asphalt was studied by Fourier transform infrared spectroscopy (FTIR) and gel permeation chromatography (GPC). The macro mechanical behavior of asphalt binder was explored through routine physical property test and rheological property test. Finally, the mechanical properties of asphalt mixture were studied through the routine test of asphalt mixture, and the relationship between the macro and micro indexes of asphalt binder and the high and low temperature performance of asphalt mixture was established through grey correlation. The test shows that the mixing mode of TLA, bio-asphalt and base asphalt is physical blending. Modifiers affect the macro mechanical properties of asphalt by changing the distribution of asphalt components, the size of molecular weight, the interaction strength and arrangement of molecules. TLA improves the performance of asphalt binder at high temperature, but weakens the low-temperature performance. The low temperature performance of TLA modified asphalt was significantly improved by adding bio-asphalt at the cost of slightly reducing the high temperature performance. When the content of bio-asphalt is 9%–12%, the bio-asphalt/TLA modified asphalt and its mixture have better performance on high and low temperature properties than that of base asphalt. The micro indexes such as aromatic ring index and weight average molecular weight are good indicators of the high temperature performance of asphalt mixture. Creep rate (m), equivalent brittle point (T1.2) and stiffness modulus (S) can reflect the low-temperature performance of asphalt mixture.